What does Genesis 40:6 mean?

Joseph rose to a position of authority under his Egyptian master, Potiphar (Genesis 39:1–6). He was unfairly jailed, based on a lie told by his master's wife, whose seduction Joseph had rejected (Genesis 39:11–15). Joseph's character and skill make him valuable even in prison (Genesis 39:21–23). Now, he has likely been in this state for several years. At some point during that stretch, the Egyptian Pharaoh's cupbearer and baker are jailed for an unspecified offense (Genesis 40:1–4). They've been there for "some time," likely more than a few years.

Strangely, both the king's former cupbearer and his former baker had powerful dreams on the same night. They're convinced that each dream means something specific, and they're right. Joseph finds the pair "troubled" or "dejected" the next morning. They cannot explain their dreams, but they know they are abnormal. That stress is obvious enough that Joseph sees it the next day. The following verses will reveal they have no way of understanding these obviously important dreams.